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A bacterial mutant with a non-functional DNA polymerase would be unable to complete which step of NER?

a.Resynthesis of the strand to fill the gap.

A bacterium with a defective RpoH sigma factor would likely be most vulnerable to which specific environmental stressor?

a.High temperature

A food-processing plant wants to sterilize pre-packaged, opaque plastic syringes. Which sterilization method would be most effective?

d.Gamma radiation, because it is ionizing and highly penetrating.

A key difference between the DNA damage caused by UV light and the damage caused by gamma radiation is that…

d.UV light creates dimers, while gamma radiation creates strand breaks and reactive oxygen species.

A major limitation of UV surface disinfection, as noted in the materials, is its…

a.low penetration, making it ineffective in shadows or on porous materials.

A mesophilic E. coli culture is abruptly shifted from 37°C to 45°C, and growth is slowed. Which stress response is most likely to be activated to manage protein damage*?

c.Synthesis of Heat Shock Proteins (HSPs) like Hsp70 to refold denatured proteins.

A mesophilic bacterium is shifted to a 15°C environment. Which two distinct mechanisms are mentioned as part of the "cold shock response"?

c.Activation of CSPs and production of cryoprotectants.

A microbe's membrane is found to be rich in saturated, straight-chain fatty acids and ether linkages. What can be inferred about its optimal growth environment and protein structure?

a.Thermophile; proteins are rigid and have a high number of salt bridges.

A patient with the genetic disease xeroderma pigmentosum (XP) has a defective NER system. This patient would be…

c.extremely sensitive to UV light, as they cannot repair pyrimidine dimers effectively.

A pre-med student is studying a Staphylococcus aureus (a mesophile) infection. Why is the patient's high fever (e.g., 40°C / 104°F) a problem for this bacterium?

a.The fever is approaching the bacteria's maximum growth temperature, which can denature its mesophilic enzymes.

A research team discovers a novel archaeon* in a 95°C hydrothermal vent. Which combination of molecular adaptations would they most expect to find __*?

c.Ether-linked membranes, high percentage of saturated fatty acids, and enzymes with a high activation energy.

A researcher exposes two identical cultures of E. coli to a sterilizing dose of UV light. Culture A is incubated in a dark room. Culture B is incubated under a bright visible-light lamp. What is the predicted outcome?

a.Culture B will show a higher survival rate due to photoreactivation.

A student analyzing the membrane of a thermophile would expect to find a high concentration of lipids that are analogous to…

d.Butter or wax-like (high saturated fats, solid at room temp), promoting rigidity.

A student incorrectly claims that psychrophiles use "an increased number of salt bridges to protect against cold." Why is this statement false, according to the provided material?.

d.Psychrophiles use fewer salt bridges to maintain flexibility, and the cold shock response involves CSPs.

A thermophilic archaeon membrane is uniquely stable due to the presence of:

c.More stable ether linkages and, in some cases, tetraether lipid monolayers.

Analysis of the DUV LED plate study (check the Image from Handout-8) for the 30s and 60s exposure times suggests that…

b.E. coli (Gram-negative) is more sensitive to DUV radiation than Listeria innocua (Gram-positive)..

Comparing repair mechanisms, NER is considered while photoreactivation is .

a.an excision and replacement; a direct reversal

How do thermophilic proteins increase structural stability at the quaternary level of proteins?

a.By forming more stable oligomers with additional subunits.

How does the cell membrane of a *psychrophile, like the "olive oil" *analogy, maintain its function in the cold?

c.By incorporating unsaturated and branched-chain fatty acids, which introduce kinks and prevent solidification.

If a researcher experimentally "saturates" the membrane lipids fats of a psychrophile (i.e., removes unsaturated fats by removing the C=C cis-double bonds to make it look like saturated fats C-C seen in butter), what will happen when the cell is placed at its optimal cold temperature?

d.The membrane will solidify, preventing transport and leading to cell death

Most thermophilic proteins are enriched with core of non-polar amino acids - Isoleucine (I), Valine (V), Tryptophan (W), Leucine (L) that are _ nature. Also thermophilic proteins also contain, some surface amino acids that is basic (Arginine and Lysine) and acidic (Glutamic acid and Aspartic acid) that have a property. What two classes of amino acids are represented by this list*?

d.Hydrophobic/non-polar and polar/hydrophilic/charged

The "adapt, survive or perish" concept can be applied to radiation exposure. Which organism survives gamma radiation by forming a dormant structure?

d. Bacillus cereus

The "indirect damage" pathway of gamma radiation involves which initial event?

b.The ionization of water molecules, creating free radicals.

The lac operon, as described in the materials, is a key example of "gene-environment interaction" because it…

c.ensures the cell only expends energy to metabolize lactose when it is environmentally present.

The components Ca-DPA (Calcium dipicolinate) and SASPs (Small Acid-Soluble Spore Proteins) are crucial for…

c.the stability and DNA protection of endospores against stresses like gamma radiation.

The formation of pyrimidine dimers is a critical mutagenic event because it directly…

d.blocks the progression of both DNA polymerase and RNA polymerase.

The Handout-8 states that thermophilic proteins have reduced glycine. What is the functional reasoning for this?

a.Glycine is the most flexible amino acid; reducing it increases the protein's structural rigidity.

The Handout-8 states thermophilic proteins have "an enrichment of hydrophobic residues (I, V, Y, W, L) and (R, E)." What is the likely purpose of this in addition to salt bridges?

b.To promote stronger hydrophobic interactions in the protein's core, increasing its stability.

The mechanism of Nucleotide-Excision Repair (NER), in Handout-8, is initiated by what enzymatic action?

b. A nuclease cleaving the phosphodiester backbone on both the 3' and 5' sides of the lesion.

The milk UV case study lists a wide variety of pathogens (Listeria, E. coli, Staphylococcus). The universal target of the UV light in all these different bacteria is their…

a.DNA.

The overall process of gene-environment interaction allows a bacterium to…

d.regulate gene expression to "adapt, survive or perish" in response to environmental cues.

What adaptations in the "cold shock response" seen in a bacteria growing at 5°C, best described ?

c.Because it involves multiple strategies, including activating CSPs to manage translation and producing cryoprotectants to prevent ice crystal formation.

What does the "perish" outcome of a gene-environment interaction imply?

a.The environmental stress is so far outside the optimal range that the organism's adaptive responses (like HSPs/CSPs) are overwhelmed.

What is the direct kinetic consequence of the rigid protein structure favored by thermophiles*?

a.It significantly reduces enzyme activity at moderate temperatures because thermophiles need higher Ea / thermal boost to work efficiently.

what is the key structural difference in the proteins (not enzymes) of a *psychrophile *compared to a *mesophile?

b.A higher number of glycine residues and a lower ratio of charged/aromatic residues.

What is the primary function of Heat Shock Proteins (HSPs) like Hsp70?